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In Network Analyst Routing, how do you get turn delays to work?

Question asked by brads98 on May 10, 2018
Latest reply on May 11, 2018 by brads98

I am trying to get turn delays to work in Network Analyst Routing.  My numbered questions are in bold below.  I have read all the articles I can find in ESRI help on turns, global turn delays, etc.

 

I created a Network Dataset from a Roads feature class.  With help on this community board, I was able to customize the Length attribute to control how the routing was done.  I did this with a Python script in Field Evaluators for the attribute.

 

Now I want to add a bigger penalty for left turns.  Question #1:  Should I care if I use global turn delays or is there a non-global turn delay?  How would I decide which I should use?

 

I thought I needed to add a Turn feature class  (Question #2:  Do I need to?  How would I decide?), so I did so with the Creature Turn Feature Class (Network Analyst) tool.  I did not use a template.

 

Then I added the Turn feature class to the Network Dataset.

 

Now I tried 10 different ways to set a longer delay for left turns using Script Evaluators for the Turns in my Length Attribute.  It always seemed to ignore what I did.  Re-building the dataset does not help.

 

Then I read (in a Community comment I think, not in help) that you have to set a time-base Cost as the Use by Default Cost Attribute to use turn delays.

 

Question #3:  Is this only true for using Global Turn Delays?

 

Question #4:  Are the non-default costs used or ignored?  Does it calculate the non-default costs, and then just make those values available for the default cost evaluation?  This does not appear to be documented at all.  I'd like to understand how all that works.

 

So I added a time-based Cost Attribute and set Use by Default.  I found the directions to get to the Global Turn Delay setting, and I tried setting all the left turn delays to a very long time (e. g., 600 seconds) so I could test a short route that could get to the destination using one or two left turns.  Screenshot of dialog attached.  No matter what I did, it always makes the route have two left turns.  It is even takes a longer route than it could.  See attached screenshot of route.  Re-building the dataset does not help. 

 

Question #5:  Am I doing the right things to get this working?  Any suggestions?

 

I'm happy to give more detail about anything I did if it will help answer my questions.

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